WASHINGTON—A group of U.S. states led by Texas have filed an amended complaint against Alphabet Inc.’s Google, accusing the tech giant of using coercive tactics and breaking antitrust laws in its efforts to boost its already-dominant advertising business. The updated allegations are the latest in an onslaught of regulatory scrutiny of Google over its practices. The tech company faces several lawsuits, including one by the Justice Department for monopolistic practices. Earlier this week, Google lost an appeal against a $2.8 billion European Union antitrust decision. The amended U.S. lawsuit, filed in a federal court in New York late Friday, accuses Google of using monopolistic and coercive tactics with advertisers in its efforts to dominate and drive out competition in online advertising. The lawsuit also highlights Google’s use of a secret program dubbed “Project Bernanke” in 2013 that used bidding data to give its own ad-buying an advantage. For example, in …